This is a hypothetical question. Suppose generics were implemented as in
the draft proposal, but without contracts. Instead, the rule is that if an
instantiation of a generic function with a specific type argument doesn't
compile, then it can't be used.
Under those circumstances, is there any way to write a function
func Min(type T) (a, b T) T {...}
that returns the smaller of its two arguments, and meets _all_ of these
criteria?
1) If a specific type X has a suitable Less() method, then Min(X) uses that.
2) Otherwise, if the < operator can be applied to X, then Min(X) uses that.
3) Otherwise, any use of Min(X) fails to compile. (A run-time panic does
not satisfy this criterion.)
By "X has a suitable Less() method", I mean that this function should
compile successfully:
func XMin(a, b X) bool {
return a.Less(b)
}
I'm fairly sure there's no way to write Min, but perhaps someone can prove
me wrong?
(With contracts I'm doubly sure it can't be done, as the contract for Min
would have to permit both Less and <, so then Min(X) would only be allowed
for types X having both Less and <.)
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